US5962849A - Particle selection method and a time-of flight mass spectrometer - Google Patents

Particle selection method and a time-of flight mass spectrometer Download PDF

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Publication number
US5962849A
US5962849A US08/826,311 US82631197A US5962849A US 5962849 A US5962849 A US 5962849A US 82631197 A US82631197 A US 82631197A US 5962849 A US5962849 A US 5962849A
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time
charged particles
particles
electric field
deflector
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US08/826,311
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Naoaki Saito
Mitsumori Tanimoto
Kazuyoshi Koyama
Yasushi Iwata
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National Institute of Advanced Industrial Science and Technology AIST
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Agency of Industrial Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/40—Time-of-flight spectrometers

Definitions

  • the present invention relates to a particle selection method of analyzing a mass of particles or selecting particles like atoms, molecules, ions, or ultrafine particles (clusters) with a high resolution, and a time-of-flight mass spectrometer as a particle selection apparatus.
  • FIG. 1 shows an example of a conventional time-of-flight mass spectrometer.
  • the mass spectrometer has an ionization laser 1, an accelerator 2, a deflector 3, a reflector 4, and an ion detector 5.
  • those neutral particles P are first irradiated by laser using the ionization laser 1 and are ionized to form charged particles (ions) Pe.
  • the charged particles Pe are accelerated only over a constant distance by a static electric field between electrodes 2a and 2b of the accelerator 2 and then are deflected by the deflector 3 in a predetermined manner.
  • a conventional time-of-flight mass spectrometer In a conventional time-of-flight mass spectrometer, charged particles with different masses do not pass the same position at the same time after the starting of the acceleration. Thus, only charged particles of a particular mass is subject to the laser irradiation in small region after the ionization. In addition, a conventional time-of-flight mass spectrometer cannot measure only charged particles with prescribed charge state.
  • an object of the present invention is to remove the above-mentioned defects and to provide a particle selection method and a time-of-flight mass spectrometer overcoming the above-mentioned defects by means of the double pulsed acceleration for a constant period of time instead of the conventional scheme of accelerating over a constant distance.
  • a particle selection method comprises the steps of:
  • the form of pulse is generated by a pulse generator.
  • the pulse generator is a rectangle pulse generator.
  • a particle selection method comprises the steps of:
  • the mass or the charged state of the charged particle is changed by a laser irradiation.
  • a time-of-flight mass spectrometer comprises:
  • a double pulsed accelerator for accelerating a plurality of charged particles to one direction by a homogeneous or spatially uniform electric field during a common finite period of time, and for subsequently accelerating the plurality of charged particles to a direction opposite to the one direction by a homogeneous or spatially uniform electric field during a common finite period of time to provide the same momentum to all of the plurality of charged particles;
  • a selector arranged at a special focus defined in relation to an output from the double pulsed accelerator for selectively outputting charged particles passing through the special focus;
  • a slit for selectively passing an output from the second deflector which is only one of stable particles having no change of mass or charge state and particles which having a specific change of charge-to-mass ratio;
  • an ion detector for measuring a time-of-flight of the charged particles from the slit.
  • the time-of-flight mass spectrometer may further comprise a excitation laser for the laser irradiation.
  • the electric field E y0 of the first deflector and the second deflector is
  • V beam is the initial velocity of the charged particle on y-axis
  • j is any integer greater than
  • d is the length of each of the first deflector and the second deflector on x-axis.
  • FIG. 1 is a schematic diagram showing an example of a conventional time-of-flight mass spectrometer
  • FIG. 2 is a schematic diagram showing an embodiment of a time-of-flight mass spectrometer in accordance with the present invention.
  • FIG. 3 is a schematic diagram showing an embodiment of a time-of-flight mass spectrometer in accordance with the present invention.
  • FIG. 2 shows the structure of an embodiment 1 of a time-of-flight mass spectrometer in accordance with the present invention.
  • the time-of-flight mass spectrometer has an ionization laser 11 for ionizing a plurality of neutral particles, and a double pulsed accelerator 12 for accelerating a plurality of the charged particles ionized by the ionization laser 11 to one direction by a homogeneous or spatially uniform electric field during a common finite period of time, as well as subsequently accelerating a plurality of charged particles to a direction opposite to the one direction by a homogeneous or spatially uniform electric field during a common finite period of time to provide the same momentum to all of the plurality of charged particles.
  • the time-of-flight mass spectrometer further has a selector 13 arranged at a special focus defined in relation to the particular position, where by the double pulsed acceleration of the double pulsed accelerator 12, all the charged particles with the same initial condition pass through at the same time independent of their mass or charge state.
  • the time-of-flight mass spectrometer also has a first deflector 15 and a second deflector 16 for deflecting stable particles of the plurality of charged particles passed through the selector 13, and a slit 17 for selectively passing and output from the second deflector 16 which is only one of the stable particles with no change of mass and charge state during the flight or the particles with a prescribed change of charge-to-mass ratio between the selector 13 and the deflector 16, and an ion detector 18 for measuring a time-of-flight of the charged particles passed through the slit 17.
  • P denotes neutral particles like molecules or ultrafine particles whose mass spectrum is to be measured
  • Pe denotes charged particles which are formed from the neutral particles P by the ionization laser 11
  • PD1 denotes the particles which have decayed or dissociated during the double pulsed acceleration and do not reach the special focus.
  • P D2 denotes charged particles which have decayed or dissociated after passing through the selector 13 before reaching at the first deflector 15
  • P D3 denotes charged particles which have decayed or dissociated after passing through the first deflector 15 before reaching at the second deflector 16.
  • the double pulsed accelerator 12 has, for example, mesh electrodes 12a and 12b. A positive voltage is first applied between the electrodes 12 and 12b and then a negative voltage is applied between the electrodes 12a and 12b to doubly accelerate the charged particles for a common finite period of time.
  • the double pulsed acceleration by the double pulsed accelerator 12 of the present invention allows the charged particles Pe with the same initial condition (initial position and initial velocity) to pass through the particular position at the particular time independent of mass or charge state of the charged particles.
  • the point in the phase space or the world of space and time specified by combination of the particular time (focus time) and the particular position (focus point) is defined as a special focus.
  • Using a selector 13 to select only the charged particles Pe passing through the special focus Ps can select only the charged particles Pe determined by initial condition. Since the charged particles P D1 has decayed and dissociated in the process of double pulsed acceleration cannot reach the focus point, those particles may be excluded.
  • the component of the velocity along the direction of the acceleration is inversely proportion to the mass while the component of velocity along the direction perpendicular to the acceleration is constant independent of the mass.
  • the first deflector 15 aligns all of those charged particles Pe to be the parallel beam, and then the second deflector 16 deflects them to pass through the predetermined point of the slit 17.
  • the flight time of the charged particles from the special focus Ps to the ion detector 18 is proportional to the mass of each of the charged particles.
  • x0.tbd.x(0) and y0.tbd.y(0) are the initial positions
  • v x0 .tbd.v x (0) and v y0 .tbd.v y (0) are components of the initial velocity.
  • a selector 13 which passes the particles through a focus point at a focus time may select only the charged particles Pe determined by the initial condition.
  • the charged particles Pe are first accelerated to the negative (left) direction along the x-axis (1a), and then (1b), accelerated to the positive (right) direction along the x-axis (1c), finally received the momentum to the positive direction as a whole (1d), have zero or negative value of X-coordinate at the time ⁇ (1e).
  • Those conditions are independent of variations of g(t) and h(t) as a function of time t.
  • the electric field along the direction of y-axis is applied by the first deflector 15 at a ⁇ x ⁇ (a+d) and the second deflector 16 at R-(a+d) ⁇ x ⁇ R-a.
  • the following equation (11) of electrostatic field is considered.
  • the conditions of the acceleration method of the present invention are the conditions comprising the followings: using the homogeneous or spatially uniform electric field, accelerating first the charged particles Pe to the negative direction along the x-axis during a common finite period of time, and then accelerating to the positive direction along the x-axis during a common finite period of time, finally giving the momentum to the positive direction along x-axis as a whole from the electric field, the charged particles have zero or negative value of X-coordinate at the time of the end of acceleration ⁇ .
  • the conditions are fully independent of variation of the electric field as a function of time.
  • the electric field in the form of pulse is applied by electrodes, for example, using a pulse generator.
  • a pulse generator especially a rectangle pulse generator.
  • the homogeneous or spatially uniform electric field is generated between the electrodes by applying the voltage using the pulse generator.
  • the pulse generator which generates rectangle pulses.
  • FIG. 3 shows the structure of an embodiment 2 of a time-of-flight mass spectrometer in accordance with the present invention.
  • the time-of-flight mass spectrometer has an ionization laser 11 for ionizing a plurality of neutral particles, and a double pulsed accelerator 12 for accelerating a plurality of the charged particles ionized by the ionization laser 11 to one direction by a homogeneous or spatially uniform electric field during a common finite period of time, and for subsequently accelerating a plurality of the charged particles to a direction opposite to the one direction by a homogeneous or spatially uniform electric field during a common finite period of time to provide the same momentum to all of plurality of the charged particles.
  • the time-of-flight mass spectrometer further has a selector 13 arranged at a special focus defined in relation to the particular position, where by the double pulsed acceleration of the double pulsed accelerator 12, the charged particles with the same initial condition pass through at the same time independent of their mass or charge state.
  • the time-of-flight mass spectrometer also has an excitation laser 14 for irradiating at the special point, a first deflector 15 and a second deflector 16 for deflecting stable particles of the plurality of charged particles passed through the selector 13, particles and a slit 17 for selectively passing and output from the second deflector 16 which is only one of the stable particles with no change of mass and charge state by laser irradiation of the excitation laser 14 at the special focus or the particles with a prescribed change of charge-to-mass ratio, and an ion detector 18 for measuring a time-of-flight of the charged particles passed through the slit 17.
  • P denotes neutral particles like molecules or ultrafine particles to be measured a mass spectrum
  • Pe denotes charged particles which are formed by means of ionizing the neutral particles P by the ionization laser 11
  • P D1 denotes the particles which has decayed or dissociated during the double pulsed acceleration and do not reach the special focus Ps.
  • P D2 denotes charged particles which have decayed or dissociated after passing through the selector 13 before reaching at the first deflector
  • P D3 denotes charged particles which have decayed or dissociated after passing through the first deflector 15 before reaching at the second deflector 16.
  • the double pulsed accelerator 12 has, for example, mesh electrodes 12a and 12b. A positive voltage is first applied between the electrodes 12 and 12b and then a negative voltage is applied between the electrodes 12a and 12b to doubly accelerate the charged particles for a constant time duration.
  • the embodiment 2 is the measurement of stability of the charged particles.
  • the charged particles after the ionization are irradiated by the laser 14 and the internal energy of the charged particles are increased.
  • the unstable charged particle P 01 or P 02 with changed the mass or charged state may not pass through the predetermined point of the slit 17 and may be excluded. Only the stable charged particle Pe with no change of the mass or charge state may be measured.
  • the measurement of charge state is conducted as the same laser irradiation as the embodiment 2.
  • the electric field for the first deflector 15 and the second deflector 16 is ##EQU16## Therefore, ##EQU17##

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US08/826,311 1996-11-05 1997-03-25 Particle selection method and a time-of flight mass spectrometer Expired - Fee Related US5962849A (en)

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JP8292838A JP2942815B2 (ja) 1996-11-05 1996-11-05 粒子選択方法および飛行時間型選択式粒子分析装置
JP8-292838 1996-11-05

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6573517B1 (en) * 1999-07-30 2003-06-03 Sumitomo Eaton Nova Corporation Ion implantation apparatus
US6815689B1 (en) 2001-12-12 2004-11-09 Southwest Research Institute Mass spectrometry with enhanced particle flux range
CN104011832A (zh) * 2011-10-21 2014-08-27 株式会社岛津制作所 质量分析仪、质谱仪和相关方法
EP2795664A4 (en) * 2011-12-23 2015-08-05 Dh Technologies Dev Pte Ltd FOCUS ON THE FIRST AND SECOND ORDERS USING FREE TIME FIELD REGIONS
GB2544647A (en) * 2015-11-10 2017-05-24 Micromass Ltd A method of transmitting ions through an aperture
CN115360078A (zh) * 2022-08-29 2022-11-18 东南大学 一种等动量与等动能加速的多通道质量选择器

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US5625184A (en) * 1995-05-19 1997-04-29 Perseptive Biosystems, Inc. Time-of-flight mass spectrometry analysis of biomolecules
US5654545A (en) * 1995-09-19 1997-08-05 Bruker-Franzen Analytik Gmbh Mass resolution in time-of-flight mass spectrometers with reflectors

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6573517B1 (en) * 1999-07-30 2003-06-03 Sumitomo Eaton Nova Corporation Ion implantation apparatus
US6815689B1 (en) 2001-12-12 2004-11-09 Southwest Research Institute Mass spectrometry with enhanced particle flux range
CN104011832A (zh) * 2011-10-21 2014-08-27 株式会社岛津制作所 质量分析仪、质谱仪和相关方法
CN104011832B (zh) * 2011-10-21 2016-11-16 株式会社岛津制作所 质量分析仪、质谱仪和相关方法
EP2795664A4 (en) * 2011-12-23 2015-08-05 Dh Technologies Dev Pte Ltd FOCUS ON THE FIRST AND SECOND ORDERS USING FREE TIME FIELD REGIONS
GB2544647A (en) * 2015-11-10 2017-05-24 Micromass Ltd A method of transmitting ions through an aperture
US9947523B2 (en) 2015-11-10 2018-04-17 Micromass Uk Limited Method of transmitting ions through an aperture
GB2544647B (en) * 2015-11-10 2020-06-17 Micromass Ltd A method of transmitting ions through an aperture
CN115360078A (zh) * 2022-08-29 2022-11-18 东南大学 一种等动量与等动能加速的多通道质量选择器
CN115360078B (zh) * 2022-08-29 2024-03-29 东南大学 一种等动量与等动能加速的多通道质量选择器

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JPH10144253A (ja) 1998-05-29

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